The goal of motor control systems is to direct an effecter to a target, a task that requires the system to manage the relationships between the goal of the action, motor commands and sensory feedback. This is a complex process that remains poorly understood. Based on recent accounts of motor control as well as our work to date, we propose a series of investigations in patients with neurologic dysfunction that will test specific hypotheses regarding the interaction of sensory and motor information in action and mental motor imagery. In service of the general goal of advancing our understanding of the relationship between motor plans and feedback in the genesis of action we propose the following: (1) To perform a series of investigations motivated by an account of motor control that incorporates internal models for motor planning and multiple mechanisms for feedback. (2) To investigate the anatomic bases of the components of the motor control and feedback systems by studying subjects with well-delineated focal brain lesions. (3) To investigate the role of sensory information in motor control and the mechanism by which the nervous system adapts to the loss of this information by studying patients with "deafferentation" secondary to peripheral nervous system lesions. The proposed investigations have both theoretical and clinical significance. From a theoretical standpoint, these studies should offer important insights into the cognitive architecture of body representations and motor control systems and their underlying anatomic bases. As there has been little systematic exploration of the motor control system in patients with focal lesions, these data will complement and extend results from other research domains. The potential clinical significance of this work is also clear. Motor deficits are a common and often disabling consequence of neural injury. Understanding the cerebral basis of motor control and the body schema is likely to contribute substantially to the development of interventions that target these representations. [unreadable] [unreadable]